In engines, a cylinder block has several different types of oil passages provided therein in order to provide lubrication to moving portions in each section of the engine, and oil fed under pressure from an oil pump is caused to flow through the oil passages.
FIGS. 39-55, as hereinafter described, illustrate a known construction.
In FIG. 39, reference number 302 denotes an engine; 304 a cylinder block; 306 a cylinder head; 308 a cylinder head cover; and, 310 an oil pan. The cylinder block 304 has a crankshaft 312 provided therein, and the crankshaft 312 is rotatably supported thereon. A larger end portion 316 of a connecting rod 314 is disposed on and connected to the crankshaft 312. A piston 320 is positioned on and linked to a smaller end portion 318 of the connecting rod 314.
As shown in FIGS. 40-43, the cylinder block 304 is formed with, e.g., three cylinders 322. In each of the cylinders 322, the piston 320 is reciprocably supported on a sleeve 324.
An oil filter 330 (FIG. 39) is mounted on a filter-mounting surface 328 of an outer portion 326 of the cylinder block 304 through a filter stand 332. Further, a sub-gallery 334 (FIG. 43) and a main gallery 336 are formed in the cylinder block 304. The sub-gallery 334 permits the oil fed under pressure from an oil pump (not shown) to be introduced to the oil filter 330. The main gallery 336 guides the oil from the oil filter 330 so as to be distributed into each section of the engine 302.
As illustrated in FIGS. 44-53, the main gallery 336 is positioned on the top of a skirt portion 338 of the cylinder block 304 adjacent to a cast or press-fit sleeve portion 340. The main gallery 336 is confined or closed at front and rear ends thereof by means of blind taps (not shown). In addition, the main gallery 336 is formed at a position spaced apart from the filter-mounting surface 328. The surface 328 is vertically oriented at the outer portion 326 of the cylinder block 304. Further, a journal-side oil passage 344, through which the oil from the main gallery 336 is introduced into a journal portion 342 of the crankshaft 312, is positioned in the central plane of the journal portion 342. A passage, to which the oil drops from the cylinder head 306, is not formed in the central plane of the journal portion 342. For this reason, in order to introduce the oil from the oil filter 330 into the main gallery 336, the cylinder block 304 is provided with: a first communication oil passage 348 communicated to a stand-mounting lower hole 346 of the filter-mounting surface 328, which hole 346 communicates with the oil filter; a second communication oil passage 350 communicated to the first passage 348 in a direction perpendicular thereto; and, a third communication passage 352 communicated to the second passage 350 in a direction perpendicular thereto, which passage 352 communicates with main gallery 336. In addition, a second communication oil passage-side blind tap-mounting portion 354 is formed at an outer end of the second passage 350 for mounting a blind tap (not shown) thereon. A third communication oil passage-side blind tap-mounting portion 356 is defined at an outer end of the third passage 352 for mounting a blind tap (not shown) thereon. In FIG. 52, a head-side oil passage 358 is provided in the cylinder block 304.
As seen from FIGS. 54 and 55, a cylindrical shaped, filter stand 332 consists of: a one side-threaded portion (external thread) 360 on one side of the filter stand 332; an opposite side-threaded portion (external thread) 362 on the other side of the filter stand 332; and, an incompletely threaded portion 364 between the aforesaid threaded portions 360 and 362. When the oil filter 330 is mounted on the cylinder block 304, the one side-threaded portion 360 is driven into a block side-threaded portion (internal thread) 366 of the cylinder block 304 until reaching the bottom of the latter threaded portion 366. In addition, the oil filter 330 is brought into threading attachment to the opposite side-threaded portion 362. In this case, the incompletely threaded portion 364 causes the filter-mounting surface 328 to project from the stand-mounting surface 366 by distance "D".
An example of such a lubricating oil passage structure is disclosed, e.g., in published Japanese Utility Model Application Laid-Open No. 63-123709. Pursuant to the structure as disclosed therein, lubricating oil passages extend sideward from one end of a cylinder block in a direction of a cylinder row so as to be positioned adjacent to water jackets which extend around engine cylinders. In addition, the lubricating oil passages are communicated at both ends thereof to lubricating oil-distributing passages. The distributing passages are intended for use in the lubrication of a main journal bearing.
An example of an oil filter-mounting structure is disclosed, e.g., in published Japanese Utility Model Application Laid-Open No. 59-119312. Pursuant to such a structure as disclosed therein, there is provided an oil filter, in which a cylindrical housing accommodates a filtering body. The housing is closed at one end, but is open at the other end. At the other end of the housing, a cover plate is fixedly attached to a cap body. The cover plate retains a seal packing. The cap body has a threaded oil outflow aperture punched through the center thereof. The cap body further has a plurality of oil inflow apertures drilled around the preceding oil outflow aperture. The periphery of the cover plate is blocked at the aforesaid open end of the housing in a fluid tight manner. In such an oil filter, the cover plate includes a falling-out-preventing section and a rib relief section. A rib of the sealing packing is inserted in an annular portion of the falling-out-preventing section.
In conventional types of lubricating oil passage structures for engines, an increased number of working or machining processes of various oil passages in the cylinder block is required. In addition, the oil passages other than the main gallery employ blind taps. This causes an inconvenience of respective increases in working costs, component costs, and component-assembling costs.
In addition, since the main gallery is positioned on the top of the skirt portion of the cylinder block, the main gallery is impossible to reinforce the side surface of the skirt portion. Therefore, a reinforcing rib must be provided on the side surface of the skirt portion. This causes another inconvenience of increased weight. Further, since the cast or press-fit sleeve portion is positioned close to the main gallery, there occurs still another inconvenience in that the material porosity is likely to link such sleeve portion and the main gallery together, with a consequential increase in rejection rate of the cylinder block. A yet further inconvenience is that, when an impregnating process is conducted in order to lower such rejection rate, then an increase in a manufacturing process and the like occurs, with a concomitant rise in cost.
Further, since the oil filter and the main gallery are spaced apart from one another by a great distance, additional oil passages must be provided for communicating the oil filter and the main gallery with one another. As a result, the working number of oil passages is increased. In addition, the oil filter projects sideways by a great distance from the outer portion of the cylinder block. This causes a further inconvenience in that the engine is made large in size, and is thus more inconveniently disposed in a vehicle.
A still further inconvenience is that, as illustrated in FIG. 44, a passage, to which the oil falls from the cylinder head, and the journal-side oil passage are impossible to coexist in the width of the journal housing section which supports the journal portion of the crankshaft.
Another inconvenience is that, as illustrated in FIG. 55, if the filter stand is excessively tightened into the cylinder block, cracking or tearing may occur at the opening edge of the stand-mounting portion of the cylinder block (as seen at "A" in FIG. 55). In addition, in order to bring the incompletely threaded portion of the filter stand into a mounting surface of the oil filter, the filter-mounting surface must be caused to project from the stand-mounting surface of the filter stand. This results in a heavy-weighted cylinder block. Further, since the incompletely threaded portion 364 free of threads must be provided at the central portion of the filter stand, then the overall length of the filter stand is made larger. This causes still another inconvenience in that the oil filter largely extends sideways from the outer portion of the cylinder block, thereby resulting in a large-scaled engine, with a concomitant increase in weight of the filter stand.